Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Allow the address and ports to be separated by a colon or period rather
than a space to permit directly pasting the output of commands such as
netstat and sockstat on the command line.

Reviewed by: net
MFC after: 1 week

Include param.h for CACHE_LINE_SIZE to unbreak the build.

o Remove an incomplete sentence.

PR: docs/156593
Submitted by: Yuri Pankov
MFC after: 1 week

The last big commit: let usr.sbin/ use WARNS=6 by default.

o) Restructure tcpdrop(8) to provide a facility to try to drop all established
connections. Including a flag to instead output a sequence of tcpdrop(8)
invocations that would accomplish the same thing, which is convenient for
scripting.
o) Make tcpdrop complain if the addresses given to it are entirely in different
address families, rather than failing silently.
o) When cross-referencing httpd(8), do not explicitly specify the apache2 port,
since the example in question is generic.

Normalize usage output.

- Remove MLINKS to nonexistant manpages
- Change some section numbers to match reality
- For MLINKS to manpages from ports, mention which port installs them

MFC after: 3 days

o Improve the example a bit.

Submitted by: hrs

Sort xrefs

o Replace OpenBSD-specific example by FreeBSD's one.

Noticed by: Daniel O'Connor

o Add handling of an IPv4-mapped IPv6 address.
o Use SYSCTL_IN() macro instead of direct call of copyin(9).

Submitted by: ume

o Move sysctl_drop() implementation to sys/netinet/tcp_subr.c where
most of tcp sysctls live.
o There are net.inet[6].tcp[6].getcred sysctls already, no needs in
a separate struct tcp_ident_mapping.

Suggested by: ume

o Implement net.inet.tcp.drop sysctl and userland part, tcpdrop(8)
utility:

The tcpdrop command drops the TCP connection specified by the
local address laddr, port lport and the foreign address faddr,
port fport.

Obtained from: OpenBSD
Reviewed by: rwatson (locking), ru (man page), -current
MFC after: 1 month